1. Field of the Invention
This invention relates to a compatibilizer having a block copolymer produced by a living radical polymerization, more particularly to a compatibilizer having a block copolymer that includes an epoxy group, and a blend polymer composition including the compatibilizer.
2. Description of the Related Art
Because the application field of polymer compositions has become increasingly extensive, the required properties of the polymer compositions may differ with respect to different applications. Thus, a variety of novel polymer compositions have been developed. Especially, much attention has been paid to blend polymer compositions, each of which includes different kinds of resins, in recent years since the blend polymer compositions may combine the properties and advantages of the different constituent resins. For example, the blend polymer composition may have reduced cost and a relatively high mechanical strength, or may be biodegradable. Therefore, a blend polymer composition is usually prepared according to a specific purpose.
For example, a pure resin of acrylonitrile-butadiene-styrene (ABS) may be replaced by a blend resin composition of ABS and polymethylmethacrylate (PMMA) to reduce cost. A pure polystyrene (PS) may be replaced by a blended polymer composition of PS and polylactic acid (PLA). Since use of PLA is able to reduce the required amount of petrochemical polymers and discharge of carbon dioxide and since PLA itself is a biodegradable polymer, the blend polymer composition of PS and PLA is more environment-friendly. Besides, polyesters, such as polyethylene terephthalate (PET), etc., are commonly used to produce beverage bottles. If such polyester could be recycled to blend with other polymers to produce a useful forming material, the amount of trash can be reduced and the recycled polyester may also have economical benefits.
Since different polymers have different chemical structures and properties, the blending of different kinds of polymers may have a compatibility problem. Accordingly, development of compatibilizers suitable for the blend polymer compositions has become increasingly important.
For example, when blending a styrene-based polymer with an aliphatic polyester to produce a blend polymer composition, a copolymer including a vinyl-based monomer unit and an epoxy group-containing monomer unit (an unsaturated acid glycidyl ester unit) is added to serve as a compatibilizer (see US patent application publication no. 2010/0160505). However, such conventional compatibilizer is a random copolymer, and not a block copolymer, and is not synthesized by a living radical polymerization. Therefore, the conventional compatibilizer has a wide molecular weight distribution, and the blend polymer compositions produced using the same may not satisfy the actual requirements in terms of mechanical properties.
When blending a styrene-based polymer with a polylactic acid-based polymer to produce a blend polymer composition, a styrene-(meth)acrylate-based block copolymer is added to serve as a compatibilizer. Such compatibilizer includes blocks having an affinity to respective constituent polymers of the blend polymer composition, so as to achieve the required compatible effect. However, there is no chemical bonding among the compatibilizer and the polymers. Therefore, although the blend polymer composition may have enhanced mechanical properties (such as impact strength) by virtue of addition of the compatibilizer, there is plenty of room for improvement in these mechanical properties. On the other hand, such compatibilizer is only useful for the blend polymer composition including the styrene-based polymer and the polylactic acid-based polymer, and thus the application of the same is limited.